Adding ridged foam to exterior

[leeboy]

Looking for input on this one.

1.) adding Ridged foam to exterior over existing siding

to add an RSI/R Value.

2.) If sealed tight will preform as a vapour barrier. (wrong side of wall)

3.) If sealed tight will act as an air barrier (good)

4.) house is 1970 and has 4mil poly not seled with accoustical sealent.

5.) leave a 3/4" gap, with strapingand add a with bug screen to allow moisture to escape (Rain Screen) allowing siding to dry. any R/RSI value left.

The Idea is to add siding and an R/RSI value. Not a Vapour Barrier